Detection and Isolation of Emetic Bacillus cereus Toxin Cereulide by Reversed Phase Chromatography

The emetic toxin cereulide is a 1.2 kDa dodecadepsipeptide produced by the food pathogen Bacillus cereus. As cereulide poses a serious health risk to humans, sensitive and specific detection, as well as toxin purification and quantification, methods are of utmost importance. Recently, a stable isotope dilution assay tandem mass spectrometry (SIDA-MS/MS)-based method has been described, and an method for the quantitation of cereulide in foods was established by the International Organization for Standardization (ISO). However, although this SIDA-MS/MS method is highly accurate, the sophisticated high-end MS equipment required for such measurements limits the method's suitability for microbiological and molecular research. Thus, we aimed to develop a method for cereulide toxin detection and isolation using equipment commonly available in microbiological and biochemical research laboratories. Reproducible detection and relative quantification of cereulide was achieved, employing reversed phase chromatography (RPC). Chromatographic signals were cross validated by ultraperformance liquid chromatography-mass spectrometry (UPLC-MS/MS). The specificity of the RPC method was tested using a test panel of strains that included non-emetic representatives of the B. cereus group, emetic B. cereus strains, and cereulide-deficient isogenic mutants. In summary, the new method represents a robust, economical, and easily accessible research tool that complements existing diagnostics for the detection and quantification of cereulide.